Analysis Of Triple-tower-four-span Suspension Bridge Structural Characteristics In Static Force

In recent years, triple-tower-four-span suspension bridge has been proposed in order to meetthe demand for the large river crossing project and the sea crossing project, even has beenadopted by Yingwuzhou Yangtze River Bridge. However, the studies on the characteristics of itsstructure are less comprehensivce than those on traditional suspension bridge andtriple-tower-double-span suspension bridge. So it is necessary to perform some studies which arerequirements for the objective practice as well as a need of the development of the bridgetheroies on it.First, the development of suspension bridge, triple-tower suspension bridge, and thesuspension bridge computation theory is briefly introduced in the paper. Then, the spatial finiteelement model according to the engineering example is established by professional finite elementanalysis software Midas/civil to analyse the static behavior and to contrast them in differentworking condition. Secondly, the differences between triple-twoer-four-span andtriple-tower-double-span bridges in the same working conditong.Last, the comparative study ofdifferences in static behavior with different constraint systems of stiffening girder is done andsome recommendations to scheme selection of stiffening girder constraint system oftriple-tower-four-span suspension bridge which can be draw upon by similar bridge structuredesigns in the future are put forward.The maximum vertical displacement of triple-tower-double-span suspension bridge isoccurred in the span center close to the middle-tower whose deformation and force are muchgreater than those of the side-tower and with low stiffness. Dead load controls the design of thecable in triple-tower-four-span bridge, but the temperature load can not control the design ofsuspender.There is a good consistency in the basic mechanical properties of the two bridges accordingto the contrast of calculation results between the two bridges, that means that the increase ofside span has no significant influence in the aspcts of force and deformation of the mainspan.However, at the same time, the maximum bending moment of the main tower and side tower getslarger, and the resistive overturning safety factor of the cable saddle in the main tower getssmaller. So the stiffness of the side tower should be increased in the design oftriple-tower-four-span.According to the studies on different constraint system of stiffening girder, it is possible torestrict the stiffening girder’s longitudinal displacement only in the middle-tower position orconsolidate it with the middle-tower, because they can effectively improve the structure’s static behavior of triple-tower-four-span suspension bridge with negligible negative effect. Althoughsetting rigidity central buckle in span center or swing jointing the stiffening girder in themiddle-tower position can also improve stiffness of the structure, they should be treatedcautiously, because a axial forces’ increment of the stiffening girder in the moving load will bebrought in by those measures. Restricting the stiffening girder’s longitudinal displacement onlyin the side-tower position or in three towers can improve the deformation of the structuralremarkably, but the effect of the force on stiffening girder will be extremely negative, so theconstraint system is not recommended.